Satellite Guidance Method Using Ground-Based Optimal Control
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Solution Overview
Problem
Low-thrust motors used for satellite orbital transfer and placement on station are inefficient, leading to prolonged transfer times and high fuel consumption, and existing control procedures are sub-optimal, lacking precision and being limited to specific orbit types, with additional challenges posed by the need for GNSS receivers and complex onboard calculations.
Innovation Solution
A guidance method based on optimal control theory that determines the thrust vector orientation and state variables on the ground, allowing for a guidance plan to be generated and downloaded to the satellite, enabling efficient and precise orbital transfer without the need for onboard GNSS receivers, and allowing for real-time adjustments and robustness against mission interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If low-thrust electric motors are used for orbital transfer, then fuel mass is reduced, but transfer time increases by one to two orders of magnitude
Solution Approach 1:
The guidance method pre-calculates the optimal thrust orientation law and state variables on the ground before satellite deployment. This preliminary action allows the satellite to execute pre-planned maneuvers that minimize both fuel consumption and transfer time, resolving the contradiction by having the optimal strategy determined in advance rather than requiring real-time onboard computation.
Solution Approach 2:
The method implements closed-loop feedback by continuously measuring the satellite's actual position and velocity, comparing them with the nominal trajectory, and automatically correcting the thrust orientation law. This feedback mechanism ensures that the satellite reaches the target orbit with minimal fuel consumption while maintaining the optimized transfer time, preventing deviations that would otherwise require additional corrective maneuvers.
2Manufacturing precision
If existing control procedures for electric motors are used, then orbital transfer can be performed, but transfer precision is insufficient and fuel consumption is excessive
Solution Approach 1:
The guidance method dynamically adjusts the thrust orientation law based on the satellite's actual state deviations from the nominal trajectory. Rather than using fixed control procedures, the method continuously optimizes the thrust direction and magnitude to achieve precise orbital placement while minimizing fuel consumption, adapting the control strategy in real-time to the actual mission conditions.
Solution Approach 2:
The method changes the control parameters (thrust orientation angles, specific impulse values) based on the satellite's evolving state and deviations from the nominal trajectory. By dynamically adjusting these parameters rather than using fixed values, the system achieves both high precision in orbital placement and optimized fuel consumption, resolving the contradiction between precision and efficiency.
3Adaptability or versatility
If existing control procedures are used, then orbital transfer is possible, but the method is limited to specific transfer types (GTO-GEO)
Solution Approach 1:
The guidance method is designed with universal applicability to any type of orbital transfer between arbitrary starting and target orbits, not limited to specific transfer types. The method uses general optimal control theory that can handle elliptical, circular, inclined, and equatorial orbits, making it a multi-functional solution that adapts to any mission requirements while maintaining high precision in achieving the target orbit.
4Extent of automation
If onboard GNSS receivers are used for real-time position determination, then autonomous control is improved, but device complexity and cost increase
Solution Approach 1:
The method uses ground-based tracking stations as intermediaries to determine the satellite's position and velocity. Instead of requiring complex onboard GNSS receivers, the ground stations measure the satellite's trajectory and communicate this information to the satellite, which then uses it for autonomous control adjustments. This intermediary approach achieves high automation without the complexity and cost of advanced onboard navigation hardware.
Solution Approach 2:
The method replaces the mechanical/electronic GNSS receiver system with a ground-based measurement and communication system. By substituting the onboard hardware complexity with ground-based infrastructure, the satellite achieves autonomous control capabilities without requiring complex receivers, reducing device complexity while maintaining automation through ground-satellite communication loops.
Data Source
AI summary
A method of guidance for placing a satellite on station comprises the following steps carried out during a predefined current cycle: A) determining on the ground a law of orientation of the thrust vector, and a history of state variables and of adjoint state variables of the satellite for the transfer from a starting orbit to a target orbit using optimal control theory, B) determining on the ground a law of evolution of the rotation of the satellite about the thrust vector, on the basis of the orientation law and of the history, C) representing according to a predetermined format the evolution of the state variables and adjoint state variables so as to obtain first parameters, D) representing according to a predetermined format a law of evolution of the rotation so as to obtain second parameters, E) concatenating the first and second parameters so as to obtain a guidance plan for the satellite, F) downloading onboard the guidance plan, G) periodically repeating according to a predefined period which is smaller than the duration of the guidance cycle: g1) reconstructing onboard the satellite a guidance instruction, g2) executing onboard the satellite the instruction by applying a closed control loop, H) measuring on the ground the real orbital trajectory of the satellite, I) repeating steps A) to H) with the trajectory measured at the end of the cycle as starting orbit of the following cycle, until the target orbit is attained.